The present invention concerns a procedure for manufacturing short-chain linear .alpha.-olefines, in particular 1-butylene, from ethylene.
These alpha-olefines have a number of special practical applications, depending on the length of the olefine chain. For instance, C.sub.12 -C.sub.20 .alpha.-olefines are used in the manufacturing of corresponding biodegradable washing materials of sulfonate and ethoxylate types. Alcohols prepared from C.sub.8 -C.sub.12 .alpha.-olefines have significant use, especially as softener alcohols. Furthermore, the use of C.sub.4 -C.sub.6 .alpha.-olefines, particularly as a copolymer together with polyethylene, has increased in recent years, with polyethylene brands made by combination catalysis (e.g. LLDPE) displacing traditional high pressure processes (LDPE) in many areas of practical application. Moreover, t-decylene is used in continuously increasing quantities in the manufacture of poly-olefine-type synthetic lubricants.
In industrially utilized manufacturing methods, preparation of 1-butylene is effected either by performing separation of butylene isomers from the C.sub.4 flow obtained on cracking, or by distilling the 1-butylene apart, e.g. from the olefine mixture produced in the manufacturing of .alpha.-olefines.
When manufacturing 1-butylene from ethylene, other oligomerizing products of ethylene are usually obtained in abundance, e.g. 2-butylene and other oligomers of varying length.
It is well-known that many catalysts can be used to oligomerize ethylene to yield olefines which have higher molecular weight. Oligomerizing is understood herein, to mean ethylene oligomerizing to become dimer, trimer, tetramer, etc., the aim being an oligomer with maximum linearity and having a double bond in alpha position.
It is a typical feature of olefine-oligomerizing reactions, that the rate of reaction and the product distribution are decisively dependent on the catalyst type, especially on the exact chemical structure of the catalyst, and on the applied reaction conditions. For instance, a drawback of well-known aluminum alkyl or aluminum alkyl/titanium halide catalysts of the "Ziegler" or "Ziegler-Natta" type, is their high reactivity and strong pyrophoric nature, although the reaction conditions (pressure, temperature) may be somewhat lower than those in the procedure of the present invention.
The previously-known catalysts of nickel phosphine type which are technically utilized in ethylene oligomerizing reactions, operate, on the other hand, in such a matter that the above-noted C.sub.12 -C.sub.20 alpha-olefines are principally obtained as reaction products.